Hi - yes, it could be.
I found this - https://prevention.ucsf.edu/research-project/methamphetamine It says that it dries the skin of the vagina, penis, and anus.
You didn't ask, but I'm going to tell you how bad this is for you. I'm not judging, but there is no way this can go anywhere but badly. If you have to dump the boyfriend in order for you not to do this, then dump the boyfriend. You deserve only the best.
We have an Addiction forum, if you haven't already found it - https://www.medhelp.org/forums/Addiction-Substance-Abuse/show/77
Please consider posting there about your drug use.
Again - no judgement, just compassion.